Piezoelectric igniter and distributor



July 25, 1967 E. HOOVER 3,332,409

PIEZOELEGTRIC IGNITER AND DISTRIBUTOR Filed Maron 16, 1965 lll/Am Z 4o26 INVENTOR. LAWRENCE E. HOOVER United States Patent O "Ice 3,332,409PIEZOELECTRIC IGNITER AND DISTRIBUTOR Lawrence E. Hoover, 2562 Sharon,Detroit, Mich. 48209 Filed Mar. 16, 1965, Ser. No. 440,246 Claims. (Cl.12S-148) ABSTRACT 0F THE DISCLOSURE A lever actuated piezoelectric sparkpump is mounted on the rotary shaft of an ignition distributor of amulticylinder internal combustion engine for rotation with the shaft andassociated distributor wiper arm. The lever has a follower portion whichruns on a sinuous circular cam track stationarily supported by thedistributor housing and oriented to stress the piezoelectric element ofthe spark pump via the lever so that firing voltage is generated by thepump in synchronism with the wiper arm passing by each of thedistributor terminals in the distributor cap for sequential firing ofthe spark plugs of the engine.

This invention relates generally to ignition systems, and moreparticularly to a piezoelectric ignition and distributor unit.

In a piezoelectric ignition system, the high voltage required for firing`the spark plugs of an internal combustion engine is derived from apiezoelectric element which is stressed in timed relation with therotation of the engine shaft. Such piezoelectric systems areadvantageous over the conventional breaker-condenser-coil ignitionsystems in that the piezoelectric systems do not draw ignition currentfrom a battery, thereby eliminating some of the load on the usualautomotive battery. The voltage supplied by the piezoelectric element ismore constant than that supplied by magnetos. Ceramic polycrystallinepiezoelectric elements are available commercially at the present timethat are capable of withstanding the relatively great stress required toproduce the high voltage needed for firing spark plugs.

An object of this invention is to facilitate conversion of the usualdistributor of a conventional battery ignition system into apiezoelectric ignition and distributor unit.

Another object of the invention is to provide a piezoelectric igniterand distributor unit which can be driven by the distributor shaft of aconventional automotive distributor. 1

A further object of the invention is to reduce transverse loading of thedriving shaft for a piezoelectric igniter and and distributor so as toreduce wear of the shaft.

Another object of the invention is to provide a mechanism forautomatically discharging the piezoelectric element of the unit when theignition is turned off.

Other objects of the invention are to reduce noise, power consumptionand time delays in a piezoelectric igniter and distributor unit.

Other objects, features and advantages of the present invention will beapparent in the following detailed description taken in conjunction withthe accompanying drawings wherein:

FIG. l is a vertical sectional view of a piezoelectric igniter anddistributor unit in accordance with the invention taken on the line 1-1of FIG. 2.

FIG. 2 is a sectional view of the unit of FIG. 1 taken on the line 2-2of FlG. l.

FIG. 3 is a fragmentary sectional view taken along line 3-3 of FIG. 2and showing a reaction roller and a cam lobe of the unit.

FIG. 4 is a top plan view of the unit of FIG. l to a reduced scale.

3,332,409 Patented July 25, 1967 structure and as an enclosure for twovertically spaced Y discs 14 and 16 which are interconnected by threeposts 18, 20 and 22 and form a rotary support structure. The discs 14,16 are rotated counterclockwise as viewed in FIG. 2 by a driving shaft24 journalled in the bottom wall 26 of housing 12 by a suitable bushing28. A sleeve 30 which projects downwardly from wall 26 is steppped downto provide a shoulder 32 to facilitate mounting unit 10 on a lixedsupport 34.

A conventional centrifugal spark advance mechanism including two weights36 and 38 is mounted between two vertically spaced support discs 40 and42. The weights 36, 38 are piloted on posts 44 and 46 axed to disc 40.Posts 41 and 43 are affixed to weights 36 and 38 respectively, and disc42 is piloted on posts 41, 43. Shaft 24 has a flange 25 connected todisc 40 and a stub shaft 4S is connected to disc 42 and is piloted on astub end of shaft 24. At constant engine speed all of the discs rotateas a unit. As engine speed varies, disc 42 and the structure includingthe spark pumps affixed to it are rotated relative to disc 40 and shaft24 by the action of the spark advance mechanism.

Another stub shaft or post is fixed to the center of disc 16. A rotor 56made of insulating material is rigidly secured to shaft Sil and has aconductor 58 afxed to its top side. A terminal screw 60 is provided forconnecting an insulated lead 62 to conductor 58. The discs 14, 16,

,40, 42 and shafts 24, 48, Si) are all made of metal. The

cup-like base 52 of housing 12 is metallic, but the cap 54 is made ofinsulating material, preferably plastic.

Firing voltage is generated by the two piezoelectric ceramic slugs 64and 66 each silvered at one end and mounted end-to-end with theirrespective silvered ends 68 and 70 abutting. Slugs 64 and 66 aremaintained in this relationship by a metal holder 72 which is fixed todisc 14. insulating material 73 extending around slugs 64, 66 isolatessilvered ends 68, 70 from the metal holder 72. An adjustitng screw 74threads into one end of the holder for positioning slugs 64 and 66axially within the holder. A pointed metal conductor 76 abuts theleft-hand end of slug 64 as viewed in FIGS. l and 2.

Slugs 64 and 66 function in known manner as capacitors, conductor 76 andscrew 74 serving as grounded capacitor electrodes and the silvered slugends 68 and 70 serving as high potential capacitor electrodes. The metalholder 72 electrically and mechanically interconnects conductor 76 andscrew 74 and is connected to ground potential via disc 14, shaft 48,disc 4t) and shaft 24..The abutting silvered ends 68 and 70 of the slugsare connected by the high voltage lead 62 to the rotor terminal screw66. Slugs 64 and 66 are thus electrically connected in parallel witheach other and mechanically connected in series. More than two slugs maybe used if desired, and a single slug can be made to Work.

Axial compression forces are 'applied to the ceramic slugs by a lever 7Sacting as a force-multiplying second class lever. The inner end Sli oflever 78 is pivotally supported on a fulcrum post 82 extending betweenand supported by discs 14 and 16. The outer end 84 of the lever isbifurcated and carries a journal pin 85 which in turn rotatably supportsa cam follower roller 86. The pointed conductor 76 bears against andrides in the vertex of the V-shaped side 87 of lever 78. Lever '78functions as an actuating means for mechanically stressing the slugs,and' the slugs and lever together serve as a spark pump. The

entire spark pump and rotor assembly rotates with the spark advancemechanism 36, 38.

As the spark pump rotates counterclockwise as viewed in FIG. 2, roller86 tracks in alternating sequence on the inner circular periphery ofdistributor housing 11 and on oneof a series of four or more cam lobes88, 90, 92 and 94 mounted on the inner Vwall o f the housing. Whenroller 86 strikes the leading edge or entrance ramp of each cam lobe,lever 78 is forcibly pivoted clockwise as viewed in FIG. 2 so that itexerts axial compression force on ceramic slugs 64 and 66. The squeezingofthe slugs causes them to acquire a charge. The voltage developed isproportional to the pressure and for most practical purposes may beregarded as appearing instantaneously. As will be explained further, theslugs also acquire a charge when they are released, and the voltagedeveloped upon releasing a pressure is opposite in polarity to thevoltage produced by squeezing. The material of the slugs may be apolycrystalline ceramic, preferably composed of metallic titanates. Theceramic is a good insulator with a relatively high dielectric constant.Thus, the slugs have rather high capacitance for their size. For aspecific available ceramic slug, if a force of 7,000 p.s.i. is exertedon the slugs, a potential of 21,000 volts will be developed between thehigh voltage lead connected to their silvered ends and the groundedouter ends of the slugs. The charge and voltage developed by compressionof the slugs will be maintained by the pressure, but some leakage willoccur. Therefore, it is desirable to discharge the slugs through a sparkplug immediately after they are compressed in order to utilize themaximum voltage available from the slugs.

Except for the short entrance and exit ramps, cam lobes 88, 90, 92 and94 are of constant radius and thus, so long as cam follower roller 86 isriding on a cam lobe, such as cam lobe 90, the high voltage potential ismainmained. Shortly after cam follower roller 86 rides up the entranceramp of cam lobe 90, the rotor 56 wipes under a terminal 96. There areeight high tension terminals 96-103 (FIG. 5) which lead through the cap54 and rotor conductor 58 and the high tension terminals constitute arotary switching device. The terminals are connected by insulated cablesto spark plugs 121-128 (FIG. As rotor 56 passes under terminal 96, rotorconductor 58 connects the charged slugs 64 and 66 to spark plug 121which then res, thereby discharging the slugs.

Cam follower roller 86 continues riding along the constant radiusportion of cam lobe 90 and then rides down the exit ramp of the camlobe. This releases slugs 64 and 66 and causes them to acquire a chargeagain, but this time the voltage developed across the slugs is of theopposite polarity. The particular slugs described above become chargedpositively when they are compressed, and after discharging, they becomenegatively charged when they are released. The negative voltage may beused to re another spark plug or it may `be simply discharged to ground.In either case, rotor conductor 58 wipes under high tension terminal 97just after cam follower roller 86 rides down the exit ramp of cam lobe90. At this time, slugs 64 and 66 are in circuit with spark plug 128 andcause it to fire, thereby discharging the slugs. The charging anddischarging sequence which has been described in connection with camlobe 90 is repeated as the cam follower roller 86 engages successive camlobes.

In FIG. 5, each of the treminals 96-103 is connected to a spark plugsince the connections for an eight cylinder engine are illustrated. Inthis case, four spark plugs are fired by negative voltage. It is to beunderstood, however, that for a four cylinder engine, terminals 97, 99,101 and 103 may be connected to ground potential.

Shaft 24 may be the usual distributor shaft which is driven by theengine crankshaft. The spark pump assembly is oriented relative to shaft24 and cam lobes 88, 90, 92 and 94 to cause each spark plug to re as theassociated pist-on is approaching the top of its compression stroke.This orientation is varied in order to retard or advance the spark inresponse to engine speed by the centrifugally actuated weights 36, 38 ofthe spark advance mechanism. The centrifugal force acting lon weights36, 38 as they revolve with shaft 24 tends to throw them outward againstthe tension of spring 37 to thereby rotate disc 42 and the structureaixed thereto relative to disc 40 and shaft 24, thereby changing theorientation of the spark pump relative to the distributor shaft.

A pair of reaction rollers 104 and 106 (FIG. 2) are rotatably supportedon posts 107 and 108 extending between and secured to discs 14 and 16 inopposed balanced relation to roller 86 to take the radial loadingimposed by roller 86, thereby relieving the center shaft 24 of thisload. Reaction rollers 104 and 106 track on the constant radius innerwall of the housing, one above and one below the cam lobes. The positionof roller 106 above cam lobe 94 is evident in FIG. 3.

The invention also provides a device for discharging slugs 64 and 66when the ignition switch 110 (FIG. S) is turned off. This device 112(FIGS. l and 5) consists of a shorting contact-or or rod 114 which israised upwardly by energizing a solenoid 116 which is connected tobattery 117. Solenoid 116 is energized byturning on (closing) theignition switch 110. The energized solenoid holds the lower end of theshorting rod spaced from the rotor (FIG. l). Turning off the ignition(opening switch deenergizes the solenoid, whereup a spring 118 urges theshorting rod downwardly until its lower end contacts the rotor. Thisconnects the high voltage electrode of the spark pump to ground, therebyshorting out the spark plugsso that ignition cannot occur and allowingthe slugs to discharge.

The piezoelectric igniter and distributor unit which has been describedcan .be assembled with and operated from the distributor shaftordinarily provided in automotive vehicles. Thus, no special auxiliaryapparatus is required to accommodate the unit. The unit itself utilizessome of the usual structure of conventional distributors to goodadvantage. The spark pump assembly is integrated with the conventionalstructure just referred to. The usual breaker points, ignition coil,capacitor and battery connections (and the attendant drain on thebattery) are eliminated. Side loading of the distributor shaft has beenminimized to reduce wear. Residual charge lon the piezoelectric elementor elements could result in iiring of one or more plugs after turningolf the ignition. This possibility is -obviated by providing analternate discharge path for the piezoelectric elements which isrendered effective when the ignition is turned off.

I claim:

1. A piezoelectric igniter and distributor unit comprising a housinghaving a cup-like base having an end wall and an annular side wall and aremovable cap closing the mouth of said base, a distributor shaftextending through said end wall yof said base, a rotary supportstructure in said housing connectedvto said distributor shaft to berotated thereby, a spark advance mechanism carried by said rotarysupport structure and located adjacent said end wall, a distributorrotor affixed to said rotary support structure and located adjacent tosaid cap and a plurality of terminals leading through said cap andhaving contact portions in said housing arranged sequentially in thepath of said rotor, `wherein the improvement comprises a spark pumpassembly carried by said rotary support structure and located betweensaid spark advance mechanism and said rotor, cam means carriedstationarily on said cup-like base and having cam lobes spaced along acircular path about the rotation axis of said rotary support structure,said spark pump assembly including a piezoelectric element havingelectrodes therefor, lever actuating means for stressing saidpiezoelectric element and having a follower portion at said circularpath for engaging said cam lobes, said cam lobes, `said lever means andsaid rotor being oriented relative to one another whereby saidpiezoelectric element is stressed by the sequential interengagement ofsaid cam lobes and said follower portion in response to rotation of saidrotary support structure relative to said housing to produce a pulsatingvoltage on said element electrodes which peaks in synchronism with saidrotor passing said cont-act portions of each of said terminals, meanselectrically connecting one electrode of said piezoelectric element tosaid rotor and electrically connecting another electrode of saidpiezoelectric element to a point of reference potential, and circuitmeans electrically connected to said one electrode of said piezoelectricelement and t-o a point of electric potential providing a discharge pathin shunting circuit relation with said terminals, said circuit meansincluding a switching device mounted on said cap operable to close andopen said shunting discharge path.

2. Ignition apparatus for a multiple cylinder spark plug ignitioninternal combustion engine comprising a closed distributor housinghaving end walls at opposite ends thereof, a distributor shaft adaptedto be rotatably driven by said engine and having one end extendingthrough one of said end walls into said housing, a plurality ofterminals adapted to be electrically connected one to each of the sparkplugs `of the engine and being supported in the other one of said endwalls and having exposed portions arr-anged in a circular row withinsaid housing, rotary support means mounted on said one end of said shaftfor rotation therewith in said housing and a distributor rotor carriedon said rotary support means and having a conductive portion disposedfor travel along said circular row, wherein the improvement comprisescam means stationarily mounted on said housing in the interior thereofhaving a plurality of cam lobes circumferentially spaced along acircular path adjacent said rotary support means, a piezoelectricelement mounted on said rotary support means for rotation therewith andhaving electrodes therefor, lever means pivotally mounted on said rotarysupport means for rotation therewith and being operably connected tosaid piezoelectric element to apply stressing force thereto, said levermeans having follower means disposed to successively engage said camlobes and thereby sequentially apply and remove stressing force to saidpiezoelectric element via said lever means in response to rotation ofsaid rotary support means relative to said cam means, means electricallyconnecting one electrode of said piezoelectric element to said rotor andconnecting another electrode of said element to a point 0f referencepotential, said lobes, said follower means and said rotor being orientedrelative to one another whereby said sequential stressing of saidelement produces a pulsating voltage on said rotor which peaks insynchronism with said conductive portion of said rotor passing each ofsaid exposed terminal portions.

3. The apparatus as set forth in claim 2 wherein said lever means isfulcrumed on said rotary support means and is operably connected to saidpiezoelectric element at a point along said lever means between saidfollower means and the fulcrum point of said lever means whereby saidlever means operates as a second class lever.

4. The apparatus as set forth in claim 2 wherein the improvement furthercomprises reaction means carried on said rotary support means forrotation therewith and track means stationarily supported by saidhousing along the path of travel of said reaction means for engagementby said reaction means to thereby balance forces applied to said rotarysupport means Iby the engagement of said follower means with said camlobes during ro* tation of said rotary support means relative to saidhousmg.

S. The apparatus set forth in claim 4 wherein said housing has anannular side wall between said end walls and said cam lobes are mountedon the interior surface lof said side wall in a path encircling saidrotary means, wherein said follower means comprises rst roller meansrotatably mounted on said lever means for rolling engagement with saidcam means, wherein said reaction means comprises second roller meansrotatably mounted on said rotary support means in spaced relation fromsai-d rst roller means, and wherein said track means comprises acylindrical portion of said side wall disposed concentric with saidrotary support means and adjacent said cam means, said second rollermeans having rolling engagement with said cylindrical portion.

References Cited UNITED STATES PATENTS 2,862,146 ll/ 1958 Kreuthmeir315- 3,009,975 11/1961 Hufferd et al 123-148 3,101,420 8/1963 Hufferd etal. 3l0'-8.7 3,202,873 8/1965 Feldman 315--209 MARK NEWMAN, PrimaryExaminer.

LAURENCE M. GOODRIDGE, Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,332,409 July 25, 1967 Lawrence E. Hoover It is hereby certified thaterror appears in the above numbered patent requiring correction and thatthe said Letters Patent should read as corrected below Column 1, line10, for "pump" read generating ignition device same column 1, line 18,column 3, lines 1, 3 and 72, and column 4, lines 9, 31 and 40, for"pump, each occurrence, read generator column l, line 19, for "pump"read spark generator column 2, line 71, for "spark pump." readpiezoelectric ignition device such as that sold under the trademark"Spark Pump" by Clevite Corporation. of Cleveland, Ohio, and referred tohereinafter as a "spark generator".

Signed and sea1ed this 5th day of November 1968.

(SEAL) Attest: Edward M. Fletcher, Jr. EDWARD J. BRENNER AttestingOfficer Commissioner of Patents

1. A PIEZOELECTRIC IGNITER AND DISTRIBUTOR UNIT COMPRISING A HOUSINGHAVING A CUP-LIKE BASE HAVING AN END WALL AND AN ANNULAR SIDE WALL AND AREMOVABLE CAP CLOSING THE MOUTH OF SAID BASE, A DISTRIBUTOR SHAFTEXTENDING THEOUGH SAID END WALL OF SAID BASE, A ROTARY SUPPORT STRUCTUREIN SAID HOUSING CONNECTED TO SAID DISTRIBUTOR SHAFT TO BE ROTATEDTHEREBY, A SPARK ADVANCE MECHANISM CARRIED BY SAID ROTARY SUPPORTSTRUCTURE AND LOCATED ADJACENT SAID END WALL, A DISTRIBUTOR ROTORAFFIXED TO SAID ROTARY SUPPORT STRUCTURE AND LOCATED ADJACENT TO SAIDCAP AND PLURALITY OF TERMINALS LEADING THROUGH SAID CAP AND HAVINGCONTACT PORTIONS IN SAID HOUSING ARRANGED SEQUENTIALLY IN THE PATH OFSAID ROTOR, WHEREIN THE IMPROVEMENT COMPRISES A SPARK PUMP ASSEMBLYCARRIED BY SAID ROTARY SUPPORT STRUCTURE AND LOCATED BETWEEN SAID SPARKADVANCE MECHANISM AND SAID ROTOR, CAM MEANS CARRIED STATIONARILY ON SAIDCUP LIKE BASE AND HAVING CAM LOBES SPACED ALONG A CIRCULAR PATH ABOUTTHE ROTATION AXIS OF SAID ROTARY SUPPORT STRUCTURE, SAID SPARK PUMPASSEMBLY INCLUDING A PIEZOELECTRIC ELEMENT HAVING ELECTRODES THEREFOR,LEVER ACTUATING MEANS FOR STRESSING SAID PIEZOELECTRIC ELEMENT ANDHAVING A FOLLOWER PORTION AT SAID CIRCULAR PATH FOR ENGAGING SAID CAMLOBES, SAID CAM LOBES, SAID LEVER MEANS AND SAID ROTOR BEING ORIENTEDRELATIVE TO ONE ANOTHER WHEREBY SAID PIEZOELECTRIC ELEMENT IS STRESSEDBY THE SEQUENTIAL INTERENGAGEMENT OF SAID CAM LOBES AND SAID FOLLOWERPORTION IN RESPONSE TO ROTATION OF SAID ROTARY SUPPORT STRUCTURERELATIVE TO SAID HOUSING TO PRODUCE A PULSATING VOLTAGE ON SAID ELEMENTELECTRODES WHICH PEAKS IN SYNCHRONISM WITH SAID ROTOR PASSING SAIDCONTACT PORTIONS OF EACH OF SAID TERMINALS, MEANS ELECTRICALLYCONNECTING ONE ELECTRODE OF SAID PIEZOELECTRIC ELEMENT TO SAID ROTOR ANDELECTRICALLY CONNECTING ANOTHER ELECTRODE OF SAID PIEZOELECTRIC ELEMENTTO A POINT OF REFERENCE POTENTIAL, AND CIRCUIT MEANS ELECTRICALLYCONNECTED TO SAID ONE ELECTRODE OF SAID PIEZOELECTRIC ELEMENT AND TO APOINT OF ELECTRIC POTENTIAL PROVIDING A DISCHARGE PATH IN SHUNTINGCIRCUIT RELATION WITH SAID TERMINALS, SAID CIRCUIT MEANS INCLUDING ASWITCHING DEVICE MOUNTED ON SAID CAP OPERABLE TO CLOSE AND OPEN SAIDSHUNTING DISCHARGE PATH.